Commit fb69c2c8 authored May 08, 2020 by Alexander Duyck Committed by Michael S. Tsirkin Jun 04, 2020

virtio-balloon: Disable free page reporting if page poison reporting is not enabled

We should disable free page reporting if page poisoning is enabled but we
cannot report it via the balloon interface. This way we can avoid the
possibility of corrupting guest memory. Normally the page poisoning feature
should always be present when free page reporting is enabled on the
hypervisor, however this allows us to correctly handle a case of the
virtio-balloon device being possibly misconfigured.

Fixes: 5d757c8d518d ("virtio-balloon: add support for providing free page reports to host")
Cc: stable@vger.kernel.org
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Link: https://lore.kernel.org/r/20200508173732.17877.85060.stgit@localhost.localdomain

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

parent 4b4e4867

drivers/virtio/virtio_balloon.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -1107,11 +1107,18 @@ static int virtballoon_restore(struct virtio_device *vdev)

		static int virtballoon_validate(struct virtio_device *vdev)
		{
		/* Tell the host whether we care about poisoned pages. */
		/*
		* Inform the hypervisor that our pages are poisoned or
		* initialized. If we cannot do that then we should disable
		* page reporting as it could potentially change the contents
		* of our free pages.
		*/
		if (!want_init_on_free() &&
		(IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) \|\|
		!page_poisoning_enabled()))
		__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
		else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
		__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);

		__virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
		return 0;

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